Precision voltage-controlled current sink tests power supplies

摘要

To discover potential power-supply problems, you must run dynamic and static tests. This simple current sink tests low- to medium-power supplies and voltage sources. In this application, the current sink can draw current of 0 to 1.5 A for an input-voltage range of 0 to 5V with a supply voltage as high as 20V. The basis of the circuit is precision op-amp IC_1, an OPA277 from Texas Instruments , which features a maximum input-offset voltage of only 100 μ,V, maximum input-bias current of 4 nA, and low drift over the temperature range of -40 to +85℃ (Figure 1). The op-amp IC compares its positive input voltage with the voltage across sense resistor R_(SENSE).